Problem: Which of the following numbers is a factor of 60? ${3,7,8,9,11}$
Explanation: By definition, a factor of a number will divide evenly into that number. We can start by dividing $60$ by each of our answer choices. $60 \div 3 = 20$ $60 \div 7 = 8\text{ R }4$ $60 \div 8 = 7\text{ R }4$ $60 \div 9 = 6\text{ R }6$ $60 \div 11 = 5\text{ R }5$ The only answer choice that divides into $60$ with no remainder is $3$ $ 20$ $3$ $60$ We can check our answer by looking at the prime factorization of both numbers. Notice that the prime factors of $3$ are contained within the prime factors of $60$ $60 = 2\times2\times3\times5 3 = 3$ Therefore the only factor of $60$ out of our choices is $3$. We can say that $60$ is divisible by $3$.